1. Field of the Invention
The present invention pertains to stamped circuitry assemblies of the type wherein conductive traces are stamped from a metal sheet, and thereafter applied by adhesive or the like to a dielectric substrate.
2. Brief Description of the Prior Art
Printed circuit board assemblies produced by photographic and the like techniques are commonly employed to provide a convenient fabrication of high density electrical circuits. However, it is frequently desireable to incorporate mechanical systems in the high density circuits. Conventional printed circuit board assemblies are not satisfactory for this application, since they have a comparatively low limit to the maximum current permissible, at least in economical forms of construction. Also, a direct connection between circuit elements lying in different planes is generally impossible, so that in such cases, additional conductors have to be introduced between circuit traces and the individual elements which do not lie in a common plane. Further, conventional printed circuit board assemblies do not provide the mechanical ruggedness necessary in hybrid electro-mechanical circuit boards, particularly when the circuit is exposed to continuous vibration in operation, especially when the circuit traces must also carry high current levels which tend to degrade the mechanical strength properties of those traces. One example of a hybrid electro-mechanical device is shown in U.S. Pat. No. 3,845,256 which describes an appliance timer having an electric motor, a series of gears and rotating members, affixed to the surface of a single plane dielectric substrate.
Accordingly, stamped metallic circuits have been developed to provide the high current capability, mechanical ruggedness, and multiplane construction needed for a given application. Examples of representative stamped metallic circuits can be found in U.S. Pat. Nos. 3,108,360; 2,971,249 and 2,969,300. Typically, the conductive traces are separately formed, being stamped from a metallic sheet, to form labyrinthian circuit paths. The paths may be joined by one or more separable linking elements to form a carrier, or to strengthen the lattice network for use during assembly of the metallic circuit. Thereafter, the metallic stamping is applied to a dielectric substrate, typically using adhesive suitable for the purpose. In U.S. Pat. No. 3,108,360, for example, the stamped metal tracing is sandwiched between two dielectric sheets to protect a majority of the conductive circuit paths from corrosion or the like degradation. A similar arrangement is found in the more recent U.S. Pat. No. 4,508,399. Again the stamped metallic surface is sandwiched between two dielectric portions which substantially enclose the circuit, protecting it from casual damage.
Although each of the above arrangements provide otherwise convenient means of electrical connection to external circuit components, improvements in the electrical connectors can be made. Also, it is desired to incorporate in an inexpensive fashion, adjustable electrical connectors of the type frequently employed in timing and other measuring circuits. Further, especially when employed in highly inductive loads, it is desirable to provide a snap action switch which provides improved circuit making stroke breaking capability. In the past, such switches have comprised discrete commercially available separate assemblies, such as those shown in U.S. Pat. No. 3,362,181. Instead of employing a discrete miniature snap action switch, it would be desirable to integrally form a snap action switch with the stamped metallic circuit, in a single operation.